1. Field of the Invention
The present invention relates to a system for inflating and deflating at least one bag, including a reservoir of an inflation fluid, at least one pump with an inlet and an outlet, means for driving the pump, means for supplying the driving means with power, means for placing the bag, the reservoir, the pump inlet and the pump outlet in communication and means for controlling the power supply means and the communication means so as to alternately inflate and deflate the bag, in which system the control means and the means providing communication are arranged so that, during inflation, the reservoir communicates with the inlet of the pump and the bag communicates with the outlet of the pump, the power supply means being in service and so that, during deflation, the reservoir communicates with the bag, the power supply means being switched off.
Such a system is used in the biomedical field, for example, and in particular for cardiac assistance, that is to say the control of a cardiac module or artificial heart. An artificial heart is formed essentially of two ventricles, each having a flexible bag containing blood, the deformation of which for aspirating and delivering this blood is controlled by the deformation of another flexible bag alternately inflated then deflated by means of a system similar to the above system, with an inflation fluid such as air or nitrogen. Such a system may also be used in an artificial breathing apparatus.
2. Description of the Prior Art
A system of the above defined type is already known from the patent application filed in the German Federal Republic No. 2 558 921
In this system, because the reservoir communicates directly with the bag, during deflation, it is necessary, so that the bag is completely emptied into the reservoir, for the latter to be able to produce a suction effect itself, which effect is obtained through the deformability of the reservoir and the spring with which it is provided. Such a characteristic however complicates the construction and use of the system. In addition, during deflation, the bag is placed suddenly in communication with the reservoir, which results in a sharp variation of the pressure of the fluid which it contains which may be prejudicial to the correct operation of the cardiac module, and rapidly fatigue the components thereof.
A system is also known, from French application No. 2 580 339 for a cardiac module of closely related type, intended to be implanted in the body of the patient. In this system, the inflation fluid is air or nitrogen from an implanted reservoir and, for inflating and deflating the two bags, a single gear pump is used whose two gears are permanently driven at high speed, as well as two distributors controlled so as to place each of the bags progressively in communication with the inlet or outlet of the pump. In this system, discontinuities may however occur, as in the preceding system, in the pressure variation of the fluid in the bag. In fact, since each distributor is controlled by means of a stepper motor controlling the useful section of the communication orifice between the bag and the inlet or outlet of the pump, the variations in section of this orifice are quantified and it may happen that for the lowest non zero value of this section, the suction, or the delivery produced by the pump in the bag remains too strong, because the latter is permanently driven at high speed. In addition, the permanent driving of the pump leads to a relatively high electric energy consumption, which is obviously a drawback in the case of a device implanted in a patient, fed for example by a battery which is also implanted.